Refactor App.tsx from god component to context-based architecture

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/hooks/use-auto-stat-block.ts

@@ -0,0 +1,17 @@
+import { useEffect } from "react";
+import { useEncounterContext } from "../contexts/encounter-context.js";
+import { useSidePanelContext } from "../contexts/side-panel-context.js";
+
+export function useAutoStatBlock(): void {
+	const { encounter } = useEncounterContext();
+	const { panelView, updateCreature } = useSidePanelContext();
+
+	const activeCreatureId =
+		encounter.combatants[encounter.activeIndex]?.creatureId;
+
+	useEffect(() => {
+		if (activeCreatureId && panelView.mode === "creature") {
+			updateCreature(activeCreatureId);
+		}
+	}, [activeCreatureId, panelView.mode, updateCreature]);
+}